Telephone-receiver circuits



Aug. 12 1924.

G. w. CARPENTER'ET AL TELEPHONE RECEIVER CIERCUI'IIS Filed Jan. 29 "1921 2 Sheets-Sheet. 1

filerm 744 6621236712??? 'l flndeli QC. Carlson (ML mtowwu G. CARPENTER ET- AL TEREPHONE RECEIVER CIRCUITS Aug. 12 1924;

Filed Jan. 29. Sheets-Sheet 2 Patented Aug. l2, 1934i.

GLENN w. CARPENTER AND wnNnnLr. L. CARLSON, or WASHINGTON, nis'rnrc'r or COLUMBIA.

TELEPHONE-RECEIVER CIRCUITS.

Application filed-January 29,1921. Serial No. 449,992.

To all whom it mar concern:

Be it known t at we, GLENN W. CAR- PENTER and WENDELL L. CARLsoN, citizens of the United States, residing at Washington, in the District of Columbia, have invented certain new and useful Improvements in Telephone-Receiver Circuits, of which the following is a specification.-

Our invention relates to telephone receiver circuits for radio-telegraphy and other uses and has for an object to prevent the deleterious effects caused by electrostatic,

' electromagnetic and direct coupling which now exists between the telephone receiving circuit and other circuits, particularly with circuits inhigh power radio receiving am-' plifiers.

A further object or our-invention is' to shield the telephone receiver circuit from strays or any other electrical disturbances from external sources.

. Great difiiculty has been encountered here-.

tofore when telephone receivers were used in conjunction with high power vacuum tube apparatus, 'due to the fact that a coupling exists between the telephone receiver circuit and other circuits in the apparatus or external circuits. This coupling, in some instances, causes a detuning of the oscillatory circuit, while in otheroases it produces oscillations in thetelephone receiver circuit which is commonly known as howling when of an audio frequency.

We will now describe in detail our shielded telephone receiver circuit which prevents the above described coupling, reference being had to the accompanying drawings in "which:

Figure 1 is a diagrammatic view of the shielded receiver combined with an ordinary hi 11 power receiving amplifier.

' igure 2 is .a perspective View of the telephone receiver, parts being broken away to more clearly show the construction,

Figure 3 is a, detail perspective view of a portion of the telephone cord, clearly showin raigement of the conductors therein,

Fig. l is a modified wiring diagram of our shielded telephone circuit, and,

Fig. 5 shows a modifiedconstruction of our telephone cord. p

With reference to the diagrammatic view shown in Figure. 1, numeral 1 refers genone construction of the cords and ar-- .du cto-r associated with the apparatus. 'shown in Figure 1, the shield connection 6 erally to any high power radio, receiving amplifier, to which is connected in the usual manner the conductors 2, 2, leading to the ordinary telephone receivers 3, 3. Surrounding the conductors 2, 2, is arranged a metallic shield 4 which is preferably electrically connected with the receiver shells as indicated at 5, 5. At the amplifier end the shield is preferably electrically connectedas indicated by numeral 6 with some point of low potential as with the low potential'circuit of the amplifier or to ground 10 as indicated in the modified wiring diagram represented in Fig. 4. It will be understood'that by a low potential point we mean a point in the circuit of practically the same potential: as

the many possible constructions of the cords and shield. It will be understood that the particular construction shown and described is to be considered in an illustrative rather than a limiting sense.

With reference to Figures'2 and 3, ordinary insulatcd conductors 2, 2, lead to conventional telephone receivers or'head set 3, 3. These conductors may be covered with the usual insulating cotton-cord covering 7 if de'- sired. Surrounding the insulated conductors and the cotton covering, if the latter is used, is a metallic casing or shield 4, which is preferably. flexible. The shield 4 may be constructed oi flexible metallic conductdrs braided to ether as represented in, Figs. 2,

the telephone receiver shells and head band as indicated at 5, 5, or any other desired electrical connection may be substituted. That portion of the shield indicatedby numeral 6 may lead to any low potential conmay be connected with the low potential circuit of the amplifier. Here also ,it will be obvious that any desired form of electrical connection between the shield and the low potential conductor, may be used. Numeral 8 refers to the ordinaryinsulating cotton cerd' covering.

The particular construction of the shielded cords does not form an essential part of our invention as it will be apparent that many difierent forms, accomplishing the same purpose, might be used. For example,

the cord might be constructed with one telephone conductor arranged within the other. As, for instance, making the outer conductor hollow to receive the inner one as would be accomplished in Fig. 3 if one of the conductors 2 is removed, the outer conductor in such a case having the same connections to the telephones and instru ments with which used as the removed conductor 2 and being preferably electrically connected tothe low potential side of the telephone circuit and to the receiver shells and head band. In such a construction the outer conductor would serve as a shield. Or to state it another way, the shield could be made to serve as one of the conductors.

This alternative construction isrepresented in Fig. 5 wherein the inner conductor 2 covered with its usual insulation is shielded -set up in the amplifier circuits. conductorsare now enclosed in a metallic shield, which'shield is preferably electrically connected with the telephoneshells and with a low potential conductor, it is apparent that the shield will prevent the couplings referred'to and therefore revent an eifective transfer of energy rom the circuit formed by the telephone conductors, thus eliminating well known annoying disturbance.

Our invention finds application in all multistage electron tube circuits connected to actuate a responsive device, in which the usual reaction must be eliminated, employed in connection with either line wire carrier wave systems or in radiov systems. By use of theinvention many additional stages of:

amplification may be employed and arranged to function without the inherent reactlon of circults which would, occur under normal circumstances.

, Having thus described our invention whet we claim and desire to secure by Letters Patent of the United States is:

1. In a telephone receiver circuit the combination of telephone cords, an amplification c rcuit and means for shielding said cords from extraneous electrical Influences comprising a metallic shield enclosing said cords substantially throughout their length and an electric connection between'said shield and said amplification circuit.

2. The combination of telephone cords, a low potential circuit, means for shielding the cords from extraneous electrical influcuit in said signal amplifying device, a sig-' nal responsive device, conductors connecting said devices, a shield surrounding said conductors substantially throughout their length, and a connection between said shield and said low potential circuit.

4:. A high power radio receiving amplifier comprising an electron tube having id, filament and plate electrodes, a tclepione receiver actuated by said amplifier, and means for shieldin the telephone receiver from extraneous 'e ectrical influences and reducing regenerative effects, said means includinga metallic shield surrounding the telephone conductors substantially through out their length and a connection between said shield and one of said electrodes.

5. A high power radio receiving amplifier, a telephone receiver associated therewith and means for shielding the telephone receiver from extraneous electrical influences, said means including ainetallic shield surrounding the telephone conductors, and an electrical connection between the shield and the tele hone receiver.

6. A igh power radio receiving amplifier having a low otential circuit, a telephone receiver associated therewith, conductors connecting said receiver with said amplifier and means for shielding the telephone receiver from extraneous electrical influences,

said means including a metallic shield surroundin the telephone conductors and an electrical connection. between the shield and the low potential circuit. 7. A high power radio receiving amplifier having a low potential circuit, a telephone head set associated therewith, and means for shieldin the telephone head set from extraneous e ectrical influences, said means including a metallic shield surrounding the telephone conductors, and electrical connectlon between the shield and the telephone head set, and an electrical connection between the shield and the low potential circuit.

8. In a radio receiving apparatus the combination of a thermionic vacuum tube amplifier, an input circuit, an output circuit,

reproducing means in said output circuit the conductors of extending subst'anand means surroundi said output circuit on tially throughout the length thereof for shielding said reproducing means from extraneous electrical influences and regenerative eii'ects.

9. In a radio receiving apparatus the comshielding said telephone receiver's from extraneous electrical influences and regenerative eiiects. r

10. In a radio receiving apparatus the combination of a lurality of thermionic vacuum tubes having id, filament and plate electrodes, circuits interconnecting said electrodes, "a source of potential for heating said filament electrodes, an output circuit including a plate electrode, telephone receivers and a source of potential and means connectedto said-source of filament potential surrounding the conductors of said circuit substantially throughout their length for shielding said telephone receivers from extraneous electrical influences and regen-.

erative eflectsa 11. In a radio receiving apparatus the combination of a thermionic vacuum tube amplifier, an input circuit, an output circuit, reproducing means in said output circuit and means maintained at ground potential surrounding the conductors of said output circuit and extending substantiall throughout the length thereof for shie din said reproducing means from extraneous e ectrical influences and regenerative effects.

12. In a radio receiving apparatus the combination of-a lurality of thermionic vacuum tubes having grid, filament and plate electrodes, an output circuit including a plate electrode, telephone receivers and a source of potential and means surrounding the conductors of said circuit and extending substantially throughout the length thereof and connected to said source of potential for. shielding said telephone receivers from extraneous electrical influences and regenera-- tive eii'ects;

13. lln a radio receiving apparatus, an electron tube amplifier comprising a lurality of electron tubes having grid,' filament and plate electrodes, an input circuit,

an output circuit, a responsive deviceconnected in said output circuit, conductors for electrically connecting said device and saidxi output circuit,'and means for shielding sai'dll conductors from extraneous electrical in fluences and regenerative action With.,said input circuit comprising a flexible metallic shield surroundin the conductors and extending substantlally' throughout their length, and an electrical connection between the shield, the responsive device, and one of said electrodes.

GLENN W. CARPENTER.

WENDELL L. CARLSON. 

